I own a home in San Francisco whose stucco is showing random rust spots. At first I thought that the stucco was not thick enough and/or the lath or fasteners were not of the proper type but now I am more inclined to believe that iron specs contaminated the sand used at the stucco material (there was a class law suit against a local sand supplier a few years ago because of this type of contamination, I was told).

I want to repaint the house and would like to make sure that I take all the right steps to make sure that the rust spots do not come back after the paint job.

I am considering using F-9 Barc and/or Rusterizer to attack the stains at first and then using two coats of a good quality primer followed by two coats of an elastomeric paint.

Has anyone at this forum faced a similar situation and what solution did you find? I would appreciate any opinion on my approach as well.
Thanks.
Cassio